feat(subagents): make subagent timeout configurable via config.yaml (#897)

* feat(subagents): make subagent timeout configurable via config.yaml

- Add SubagentsAppConfig supporting global and per-agent timeout_seconds
- Load subagents config section in AppConfig.from_file()
- Registry now applies config.yaml overrides without mutating builtin defaults
- Polling safety-net in task_tool is now dynamic (execution timeout + 60s buffer)
- Document subagents section in config.example.yaml
- Add make test command and enforce TDD policy in CLAUDE.md
- Add 38 unit tests covering config validation, timeout resolution, registry
  override behavior, and polling timeout formula

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

* feat(subagents): add logging for subagent timeout config and execution

- Log loaded timeout config (global default + per-agent overrides) on startup
- Log debug message in registry when config.yaml overrides a builtin timeout
- Include timeout in executor's async execution start log
- Log effective timeout and polling limit when a task is dispatched
- Fix UnboundLocalError: move max_poll_count assignment before logger.info

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

* ci(backend): add lint step and run all unit tests via Makefile

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

* fix lint

---------

Co-authored-by: Claude Sonnet 4.6 <noreply@anthropic.com>

config.example.yaml

@@ -192,6 +192,23 @@ sandbox:
 #   use: src.community.aio_sandbox:AioSandboxProvider
 #   provisioner_url: http://provisioner:8002
 
+# ============================================================================
+# Subagents Configuration
+# ============================================================================
+# Configure timeouts for subagent execution
+# Subagents are background workers delegated tasks by the lead agent
+
+# subagents:
+#   # Default timeout in seconds for all subagents (default: 900 = 15 minutes)
+#   timeout_seconds: 900
+#
+#   # Optional per-agent timeout overrides
+#   agents:
+#     general-purpose:
+#       timeout_seconds: 1800  # 30 minutes for complex multi-step tasks
+#     bash:
+#       timeout_seconds: 300   # 5 minutes for quick command execution
+
 # ============================================================================
 # Skills Configuration
 # ============================================================================